Golf club heads come in many different forms and makes, such as wood- or metal-type, iron-type (including wedge-type club heads), utility- or specialty-type, and putter-type. Each of these styles has a prescribed function and make-up. For example, iron-type and utility-type golf club heads generally include a front or striking face, a top line, and a sole. The front face interfaces with and strikes the golf ball. The angle between the face and a vertical plane is called the loft angle.
A plurality of grooves, sometimes referred to as “score lines,” may be provided on the face to assist in imparting spin to the ball. A portion of the face may have an area with a different type of surface treatment that extends fractionally beyond the score line extents. In addition, the top line is generally configured to have a particular look to the golfer and to provide structural rigidity for the striking face. Some club heads have the surface treatment wrap onto the top line. The sole of the golf club is particularly important to the golf shot because it contacts and interacts with the ground during the swing.
In conventional sets of iron-type golf clubs, the club heads are attached to a shaft, which has a grip attached to the other end. The set generally includes irons that are designated number 3 through number 9, and a pitching wedge. Higher loft angle clubs are generally called “short irons” because the higher loft angle results in a shorter overall shot distance. Lower loft angle clubs are generally referred to as “long irons” because these types of clubs usually result in a longer overall distance. Each iron has a shaft length that usually decreases through the set as the loft for each club head increases from the long irons to the short irons. One or more additional long irons, such as those designated number 1 or number 2, and wedges, such as a gap wedge, a sand wedge, and a lob wedge, may optionally be included with the set. Alternatively, the set may include irons that are designated number 4 through number 9, a pitching wedge, and a gap wedge.
The overall weight of each club head generally increases through the set as the shaft length decreases from the long irons to the short irons. To properly ensure that each club has a similar feel or balance during a golf swing, a measurement known as “swingweight” is often used as a criterion to define the club head weight and the shaft length. Because each of the clubs within the set is typically designed to have the same swingweight value for each different lofted club head or given shaft length, the weight of the club head is confined to a particular range.
The length of the shaft, along with the club head loft, moment of inertia, and center of gravity location, impart various performance characteristics to the ball's launch conditions upon impact and dictate the golf ball's launch angle, spin rate, flight trajectory, and the distance the ball will travel. For example, flight distance generally increases with a decrease in loft angle and an increase in club length. However, difficulty of use also increases with a decrease in loft angle and an increase in club length.
Iron-type golf clubs generally can be divided into three categories: blades and muscle backs, conventional cavity backs, and modern multi-material cavity backs. Blades are traditional clubs with a substantially uniform appearance from the sole to the top line, although there may be some tapering from sole to top line. Similarly, muscle backs are substantially uniform, but have extra material on the back thereof in the form of a rib that can be used to lower the club head center of gravity. A club head with a lower center of gravity than the ball center of gravity facilitates getting the golf ball airborne. Because blade and muscle back designs have a small sweet spot, which is a term that refers to the area of the face that results in a desirable golf shot upon striking a golf ball, these designs are relatively difficult to wield and are typically only used by skilled golfers. However, these designs allow the skilled golfer to work the ball and shape the golf shot as desired.
Cavity backs move some of the club mass to the perimeter of the club by providing a hollow or cavity in the back of the club, opposite the striking face. The perimeter weighting created by the cavity increases the club's moment of inertia (a measurement of the club's resistance to torque), thus producing a more forgiving club with a larger sweet spot. The decrease in club head mass resulting from the cavity also allows the size of the club face to be increased, further enlarging the sweet spot. As such, these clubs are easier to hit than blades and muscle backs, and are therefore more readily usable by less-skilled and beginner golfers.
Modern multi-material cavity backs are the latest attempt by golf club designers to make cavity backs more forgiving and easier to hit. Some of these designs replace certain areas of the club head, such as the striking face or sole, with a second material that can be either heavier or lighter than the first material. These designs can also contain deep undercuts, which stem from the rear cavity, or secondary cavities. By incorporating materials of varying densities or providing cavities and undercuts, mass can be freed up to increase the overall size of the club head, expand the sweet spot, enhance the moment of inertia, and/or optimize the club head center of gravity location. However, due to construction limitations or requirements, some of these designs inadvertently thicken the top portion of the club head. Still, these improvements make the multi-material cavity back design the easiest of all styles to hit, and are ideally suited for the less adroit or novice golfer.
As mentioned above, producing a low center of gravity in a club head increases its playability. One of the ways to lower the center of gravity is to lower the face profile of the head. However, this produces a club head with a bad aesthetic appearance. Another method of reducing the club's center of gravity is to reduce the height of the hosel. However, there are disadvantages to reducing the hosel height, such as: reduced moment of inertia (since hosel mass is far away from the center of gravity); shaft-bonding concerns; and the inability to customize the club head via bending for loft/lie. In addition, many golfers dislike the appearance of a club head that has a very small hosel.
As such, there remains a need in the art for a club head that has a modified top line such that the resulting club has a desirable center of gravity location and remains aesthetically appealing to the golfer.